Ore and Alteration Types of the Gold and Copper Mineralization in the Lascogon Project, Surigao del Norte, Mindanao Island, Philippines

Two ore and three alteration types were identified in the Lascogon Project of Philex Gold Philippines, in Surigao del Norte, Mindanao Island, Philippines. The jasperoid ore is the host to the Carlin‐like gold mineralization in the Lascogon and Danao prospects. The ore occurs in a decalcified and silicified horizon, with minor chlorite and goethite, stibnite, pyrite and quartz crystals ranging from cryptocrystalline to botryoidal. The stringer–stockwork type Cu‐Au mineralization in the Suyoc prospect is hosted in argillized andesitic rocks of the Mabuhay Formation. The primary ore minerals are chalcopyrite with minor amounts of sphalerite. The alteration types identified are propylitic alteration, argillic alteration and silicification. The propylitized basaltic and andesitic flows of the Bacuag Formation bound the jasperoid mineralization in the Lascogon prospect. Stratigraphically, the relationship between propylitized basalts and stringer–stockwork Cu‐Au is not clear but a lateral change can be inferred from jasperoid in the center and stringer–stockwork towards the east.     

Lava effusion rate definition and measurement: a review

Measurement of effusion rate is a primary objective for studies that model lava flow and magma system dynamics, as well as for monitoring efforts during on-going eruptions. However, its exact definition remains a source of confusion, and problems occur when comparing volume flux values that are averaged over different time periods or spatial scales, or measured using different approaches. Thus our aims are to: (1) define effusion rate terminology; and (2) assess the various measurement methods and their results. We first distinguish between instantaneous effusion rate, and time-averaged discharge rate. Eruption rate is next defined as the total volume of lava emplaced since the beginning of the eruption divided by the time since the eruption began. The ultimate extension of this is mean output rate, this being the final volume of erupted lava divided by total eruption duration. Whether these values are total values, i.e. the flux feeding all flow units across the entire flow field, or local, i.e. the flux feeding a single active unit within a flow field across which many units are active, also needs to be specified. No approach is without its problems, and all can have large error (up to ∼50%). However, good agreement between diverse approaches shows that reliable estimates can be made if each approach is applied carefully and takes into account the caveats we detail here. There are three important factors to consider and state when measuring, giving or using an effusion rate. First, the time-period over which the value was averaged; second, whether the measurement applies to the entire active flow field, or a single lava flow within that field; and third, the measurement technique and its accompanying assumptions.     

A high-resolution operational forecast system for oil spill response in Belfast Lough

This paper presents a high-resolution operational forecast system for providing support to oil spill response in Belfast Lough. The system comprises an operational oceanographic module coupled to an oil spill forecast module that is integrated in a user-friendly web application. The oceanographic module is based on Delft3D model which uses daily boundary conditions and meteorological forcing obtained from COPERNICUS and from the UK Meteorological Office. Downscaled currents and meteorological forecasts are used to provide short-term oil spill fate and trajectory predictions at local scales. Both components of the system are calibrated and validated with observational data, including ADCP data, sea level, temperature and salinity measurements and drifting buoys released in the study area. The transport model is calibrated using a novel methodology to obtain the model coefficients that optimize the numerical simulations. The results obtained show the good performance of the system and its capability for oil spill forecast.     

Meteorites from the Lut Desert (Iran)

We present for the first time a detailed report on the discovery of a new meteorite collection region in the Lut Desert, eastern–southeastern Iran, describing its geological, morphological, and climatic setting. Our search campaigns, alongside with the activity of meteorite hunters, yielded >200 meteorite finds. Here, we report on their classification, spatial distribution, and terrestrial weathering. All the collected meteorites are ordinary chondrites (OCs). The most abundant by far are the highly weathered paired H5 distributed in the northwest of Kalut area (central Lut, Kerman dense collection area). The second are well‐preserved paired L5 also found in Kalut region. A detailed study of the geochemistry and mineralogy of selected meteorites reveals significant effects of terrestrial weathering. Fe,Ni metal (hereafter simply metal) and troilite are transformed into Fe oxyhydroxides. A rather unusual type of troilite weathering to pyrite/marcasite is observed in most of the Lut Desert meteorites. Magnetic measurements and X‐ray diffractometry confirm the occurrence of terrestrial weathering products, with the dominance of maghemite, goethite, and hematite. Mobile elements, such as Li, Sr, Mo, Ba, Tl, Th, and U, are enriched with respect to fresh falls. Meanwhile, a decrease in the V, Cr, Co, Rb (and possibly Fe) due to terrestrial weathering is detectable. The total carbon and CaCO₃ is higher than in samples from other hot deserts. The weathering effects observed in the Lut Desert OCs can be used as distinctive indicators to distinguish them from meteorites from other regions of the Earth. Measurements of terrestrial age (¹⁴C) show a range of 10–30 ka, which is in the range of ages reported for meteorites from other hot deserts except the Atacama Desert (Chile). Considering the high potential of the Lut Desert in meteorite preservation, systematic works should lead to the discovery of more samples giving access to interesting material for future studies.     

Late Holocene climate and environment of the SE Pampa grasslands,Argentina, inferred from biological indicators in shallow,freshwater Lake Nahuel Rucá

We analyzed pollen, non-pollen palynomorphs (NPPs), calcareous microfossils, plant macrofossils, diatoms, chrysophyte cysts, opal phytoliths and organic matter content in a 123-cm sediment sequence from Nahuel Rucá Lake, a shallow, freshwater system in the southeastern Pampa grasslands, Argentina. Three stages in the lake evolution were identified. Before 3,680 cal year BP, only pollen, NPPs (dinoflagellate cysts and acritarchs) and ostracods were recovered, suggesting brackish/saline conditions in the lake and nearby areas. Freshwater conditions are, however, indicated by Myriophyllum, Pediastrum and Zygnemataceae. The brackish/saline conditions could have been caused by marine influence during a Holocene sea level high stand that affected the area ca. 6,000 year BP. Between 3,680 and 390 cal year BP, macrophyte pollen and plant macrofossils indicate increasingly freshwater conditions in the lake and the adjacent area. Diatom and ostracod assemblages, however, suggest brackish and oligotrophic conditions, giving way to freshwater and meso-eutrophic conditions toward the end of this period. The relationship between submersed macrophytes (Myriophyllum, Potamogeton, Ceratophyllum, Chara) and planktonic algae (Chlorophyta and diatoms), suggests a shift in the lake from a clear to a turbid state. This turbid state is more evident after 390 cal year BP. High values of Pediastrum, Scenedesmus and diatoms (Cyclotella meneghiniana, Aulacoseira granulata, A. muzzanensis) observed during this stage could have reduced light penetration, with consequent loss of submersed plants. Pollen and plant macrofossils in the uppermost 20 cm indicate a shallow, freshwater lake similar to present, though an increase in brackish/freshwater diatoms suggests an increase in salinity, perhaps related to periodic droughts. Opal phytoliths yield a regional paleoclimatic reconstruction that agrees closely with inferences made using pollen, mammals and sediment characteristics.     

Morphotaxonomy and seasonal distribution of planktonic and benthic Prorocentrales in Karachi waters, Pakistan Northern Arabian Sea

Morphotaxonomy and seasonal abundance of dinoflagellates of the genera Prorocentrum and Mesoporos(Prorocentrales) were studied from nutrient-rich waters,Karachi Harbor and the mouth of the Manora Channel,Pakistan during May 2002-July 2003.Using both light and scanning electron microscopy,13 species of Prorocentrales were identified according to cell shape,size,ornamentation of thecal plates,and architecture of apical platelets,apical pore area,marginal pores,and intercalary bands.P.sigmoides,P.arcuatum,P.scutellum,P.donghaiense,P.balticum,P.minimum,P.emarginatum,P.lima,P.faustiae,and Mesoporos perforatus constitute new records for sindh coast of Pakistan.The most abundant species were P.minimum/P.balticum(4.5×103 cells/L),P.micans(1.1×103 cells/L),P.gracile/P.sigmoides(2.5×102 cells/L) and P.donghaiense(6.6×103 cells/L) at temperatures of 29-31℃ and salinities of 35-40.Maximum abundance was observed in winter and lower abundance in summer.There was no significant change in the distribution of species between stations except for the benthic species which occurred close to Karachi Harbor waters.Significant positive correlations were observed between Prorocentrum spp.and temperature(R 2 =0.27) and negative correlations with salinity(R 2 =-0.32) except for P.minimum and P.emarginatum which has negative correlation with temperature(R 2 =-0.24) and positive with salinity(R 2 =0.08,0.19).The finding of potential okadaic-acid producing species of benthic Prorocentrum call for monitoring for possible human health problems in this region.     

Stream temperature response to variable glacier coverage in coastal watersheds of Southeast Alaska

We measured stream temperature continuously during the 2011 summer run‐off season (May through October) in nine watersheds of Southeast Alaska that provide spawning habitat for Pacific salmon. The nine watersheds have glacier coverage ranging from 0% to 63%. Our goal was to determine how air temperature and watershed land cover, particularly glacier coverage, influence stream temperature across the seasonal glacial meltwater hydrograph. Multiple linear regression models identified mean watershed elevation (related to glacier extent) and watershed lake coverage (%) as the strongest landscape controls on mean monthly stream temperature, with the weakest (May) and strongest (July) models explaining 86% and 97% of the temperature variability, respectively. Mean weekly stream temperature was significantly correlated with mean weekly air temperature in seven streams; however, the relationships were weak to non‐significant in the streams influenced by glacial run‐off. Streams with >30% glacier coverage showed decreasing stream temperatures with rising summer air temperatures, whereas those with <30% glacier coverage exhibited summertime warming. Glaciers also had a cooling effect on monthly mean stream temperature during the summer (July through September) equivalent to a decrease of 1.1 °C for each 10% increase in glacier coverage. The maximum weekly average temperature (an index of thermal suitability for salmon) in the six glacial streams was substantially below the lower threshold for optimum salmon growth. This finding suggests that although glaciers are important for moderating summer stream temperatures, future reductions in glacier run‐off may actually improve the thermal suitability of some glacially dominated streams in Southeast Alaska for salmon. Copyright © 2013 John Wiley & Sons, Ltd.     

Backtracking drifting objects using surface currents from high-frequency (HF) radar technology

In this work, the benefits of high-frequency (HF) radar ocean observation technology for backtracking drifting objects are analysed. The HF radar performance is evaluated by comparison of trajectories between drifter buoys versus numerical simulations using a Lagrangian trajectory model. High-resolution currents measured by a coastal HF radar network combined with atmospheric fields provided by numerical models are used to backtrack the trajectory of two dataset of surface-drifting buoys: group I (with drogue) and group II (without drogue). A methodology based on optimization methods is applied to estimate the uncertainty in the trajectory simulations and to optimize the search area of the backtracked positions. The results show that, to backtrack the trajectory of the buoys in group II, both currents and wind fields were required. However, wind fields could be practically discarded when simulating the trajectories of group I. In this case, the optimal backtracked trajectories were obtained using only HF radar currents as forcing. Based on the radar availability data, two periods ranging between 8 and 10?h were selected to backtrack the buoy trajectories. The root mean squared error (RMSE) was found to be 1.01?km for group I and 0.82?km for group II. Taking into account these values, a search area was calculated using circles of RMSE radii, obtaining 3.2 and 2.11?km² for groups I and II, respectively. These results show the positive contribution of HF radar currents for backtracking drifting objects and demonstrate that these data combined with atmospheric models are of value to perform backtracking analysis of drifting objects.